ML19256E845

Responds to 790626 Ltr Re Inadvertent Scrams & Safety Injections During Surveillance.Common Mode Failure Did Not Contribute to Events Described

ML19256E845
Person / Time
Site:	Arkansas Nuclear
Issue date:	11/07/1979
From:	Trimble D ARKANSAS POWER & LIGHT CO.
To:	Reid R Office of Nuclear Reactor Regulation
References
1-119-3, NUDOCS 7911150383
Download: ML19256E845 (3)

Text

s j ARKANSAS POWER & LIGHT COMPANY POST OFFICE BOX 551 LITTLE ROCK, ARKANSAS 72203 (501) 371-4000 November 7, 1979 1-119-3 2-119-2 Director of Nuclear Reactor Regulation ATTN: Mr. Robert W. Reid, Chief Operating Peactors Branch #4 U. S. Nuclear Regulatory Commission Washington, D.C. 20555

Subject:

Arkansas Nuclear One - Units 1 & 2 Docket Nos. 50-313 & 50-368 License Nos. DPR-51 & NPF-6 Inadvertent Scrams and Safety Injections During Surveillance (File: 1510, 2'-1510)

Gentlemen:

In response to the request of Mr. D. G. Eisenhut's letter dated June 26, 1979, Arkansas Power and Light Company (AP&L) has completed a review of the events described in the request letter and has determined that similar events (i.e. inadvertent reactor scrams and/or safety injection system actuations due to operator errors during completion of surveillance re-quirements) have occurred at our facilities, Arkansas Nuclear One - Units 1 & 2 (ANO-1 & AN0-2), as indicated in Attachment 1. We feel the small number of such occurrences and the decreasing frequency indicate our operators and supervisors are aware of the importance associa %c with sur-veillance requirements and they do not exhibit the " apparent sense of complacency" for which there is statement of concern in the request letter.

With egard to the request that a determination be made as to whether similar occurrences could occur, and whether the potential exists for pro -

blems relative to such occurrences, AP&L feels that based upon the informa-tion provided, comon mode failure did not contribute to the events described. We recognize that independent random failures will always remain a possibility, however, plant design and existing surveillance and quality assurance requirements provide reasonable certainty that potential failures will be detected and corrected to provide high assurance of the reliability of safety related systems.

1M5 265 Existing management policies and procedures have been reviewed to ensure that events similar to those described in the request letter would be vigor-ously pursued and analyzed to identify potential failure modes not previous-ly considered that could lead to a significant reduction in the ability of safety systems to function as required. Licensee Event Reports (LER's) are utilized by AP&L to describe and report event of significance which could

.iave the potential of signifying previously unconsidered failure modes.

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All LER's are reviewed by both the Plant Safety Comittee and Safety Review Committee. Copies of these reports are also reviewed by the General Manager of ANO and by the Manager of Licensing. Further, the reports are reviewed by AP&L's Availability Engineering section for the specific purpose of identifying developing trends. Additionally, we presently review the Edison Electric Instituta Nuclear Power Sub-comittee Abnormal Occurrence Reports in an effort to identify poten-tial failure modes not previously considered for ANO. Based on these reviews, we feel that current company policies and procedures provide adequate assurance that all significant plant occurrences receive thorough evaluation and due consideration.

The management of ANO and its operators and supervisors recognize the need to avoid challenges to the protective features of the plants and have incorporated into the surveillance procedures those cautions which they felt were necessary to accomplish that objective. The fact that we have not had an event of the type described in the request letter coupled with our recent reviews cf these and other procedures has rein-forced our opinion that all appropria'.e cautions are currently included.

Very truly yours,

,IuC Lmd C Y k David C. Trimble Manager, l.icensing DCT:ata 1335 266

ATTACHMENT 1 s

Arkansas Nuclear One - Unit 1 Date Transient Cause 6/06/75 Reactor Trip An Instrumentation Technician working at a Reactor Building penetration caused, through wire movement, an erroneous Reac-tor Coolant Loop B Tc signal to be fed as input to the Integrated Control System (ICS) which pulled control rods to correct for TAVG-7/03/75 Reactor Trip An Instrumentation Technician grounded the TH signal during quarterly calibration.

7/23/75 Reactor Power An Instrumentation Technician grounded a Runback feedwater flow circuit during unrelated 83% - 50% work.

7/08/76 Reactor Trip An Instrumentation Technician shorted the Non Nuclear Instrumentation power supply which caused a loss of the Integrated Con-trol System component control.

4/25/77 Turbine Trip & An Instrumentation Technician shorted the Manual Reactor Balance of Plant (B0P) circuitry power Trip supply which led to erroneous hotwell level indication.

Arkansas Nuclear One - Unit 2 ANO-2 has not yet completed the testing required prior to comnercial opera tion. While some similar events have occurred, the same manage-ment policies and similar procedures will govern this unit and we ex-pect to achieve the same success.

1335 267